Agricultural air seeders include generally an implement frame and a plurality of furrow openers spaced across a width of the frame, and movable to a lowered operating position where the furrow openers engage the ground to create furrows as the frame moves along a field. Agricultural products such as seed, fertilizer, and the like are carried in tanks mounted on the frame or a cart pulled with the frame and distributed to the furrow openers by a product distribution system where one or more fans create one or more air streams and metering devices dispense the agricultural products into the air streams and the products are carried through an air distribution network made up of conduits and manifolds to the furrow openers, and then into the furrows. Furrow opener assemblies often create two (or more) separate furrows, and separate air streams carrying different agricultural products are connected so as to deposit the different products in the separate furrows.
There are different types of product distribution systems used on present day air seeders. In a Class A product distribution system, all agricultural products destined for a given furrow are metered into a single air stream in a primary supply conduit connected to a primary manifold. Such manifolds are generally a thin cylinder with an inlet in a top or bottom of the cylinder connected to the supply conduit to receive the air stream carrying agricultural products, and a number of outlet ports equally spaced around a circumferential wall. Flat fan manifolds are also known where the supply conduit directs the product air stream into one end of the a flat manifold body which divides the product air stream into channels with ports at the ends of the channels on the opposite end of the manifold body. Delivery conduits are connected to each port to carry the air stream further downstream to another manifold or to a furrow opener as the case may be.
In a Class A product distribution system the primary manifold provides primary division of the air stream and the agricultural products carried therein by dividing and directing the air stream into a number of different delivery conduits, each of which is in turn connected to a secondary manifold. The secondary manifold provides secondary division of the air stream and the agricultural products carried therein by dividing and directing the air stream into a number of different secondary conduits, each of which is connected to a furrow opener to direct the air stream, and the agricultural products carried therein, into a selected furrow.
In a Class B product distribution system the metering device itself is divided into a number of sections such that primary division of the agricultural products takes place prior to the products entering the air stream. Each conduit from a meter section is connected to a manifold which provides secondary division of the air stream and the agricultural products into a number of different secondary conduits, each of which is connected to a furrow opener as in the Class A system.
In a Class C system, all division of the agricultural products takes place at the metering device. The metering device is divided into a number of sections equal to the number of furrow openers, and a single conduit connects each meter section with each furrow opener.
Present day air seeders are often 80 or more feet wide, and a problem arises when a strip of a field to be seeded is much narrower than the seeder, as a considerable width of the field will be overlapped and seeded twice. It is most undesirable to leave even a narrow strip of a field unseeded as without crop competition weeds will flourish in the strip providing seed for future years weed growth. Seeding the adjacent field area twice however wastes valuable seed and fertilizer, and the crop on the twice seeded field area generally has reduced yield and/or quality.
Thus, it is desirable to provide a means to stop the delivery of agricultural products to furrow openers in the overlap area by providing individual control of the delivery of agricultural products to a number of different sections of furrow openers across the width of the air seeder. U.S. Pat. No. 7,690,440 to Dean et al. discloses a Class B product distribution system where the metering device is divided into a number of sections, and where gates are provided at each meter section that may be opened or closed to start or stop product flow from each meter section. The air seeder is configured so that each meter section supplies agricultural products to a downstream manifold and from there to furrow openers that are laterally arranged in order across a section of the width of the seeder so that stopping product flow to any manifold stops product flow to a section of the air seeder. Thus, as the strip of field to be seeded narrows to less than the width of the air seeder, product delivery is stopped to sections of the air seeder passing over previously seeded ground.
Commonly owned U.S. Pat. Nos. 8,690,488 and 9,295,191, the disclosures of which are hereby incorporated by reference, are directed to a system and method for operating an air seeder to ensure that air speed is maintained above a critical product transport velocity in the distribution network as ports are closed and opened, and to clear agricultural products from delivery conduits and manifolds downstream of a closed or blocked port. This system and method makes use of valves that are either in the fully open or fully closed position to accomplish their control function.